Thermoplastic polyurethanes (TPU) are fundamentally the reaction products of polyisocyanates and hydroxyl terminated intermediate, for example, diols, and in some embodiments, long-chain diols. They comprise a broad family of compositions having both urethane segments and non-urethane segments. Thermoplastic polyurethanes generally have no, or only very slight, crosslinking and accordingly have a linear structure. Thermoplastic polyurethanes are well known to the person skilled in the art and are described by way of example in Kunststoff-Handbuch [Plastics handbook], Volume 7, Polyurethane, ed. G. Oertel, 2nd edn., Carl Hanser Verlag, Munich, 1983, particularly on pages 428, 473. Some thermoplastic polyurethanes, and their preparation, are disclosed in U.S. Pat. Nos. 4,542,170 and 4,397,974. U.S. Pat. No. 4,397,974 discloses preparation of thermoplastic polyurethane elastomers by reacting a long-chain polyol having molecular weight in the range of about 400 to 10,000, preferably 800 to 6,000; with a polyisocyanate, preferably a diisocyanate; and a chain extender having a molecular weight of up to about 400. The preferred chain extenders are short-chain polyols having molecular weight of up to 380. The equivalent ratio of isocyanate groups to the active hydrogen atoms, or the NCO/OH ratio, is in the range of 0.90 to 1.10, preferably in the range of 0.98 to 1.04.
Thermoplastic polyurethanes are often used in blends with other materials, including polyolefins. However it is often difficult to achieve a blend of thermoplastic polyurethanes and other materials, including polyolefins, that retain all of the physical properties desired for the blend.
U.S. Pat. No. 4,883,837 describes a thermoplastic compatible blended composition comprising a. from 15 to 60 weight percent of a polyolefin, b. from about 30 to 70 weight percent of a thermoplastic polyurethane and c. from about 10 to 35 weight percent of a least one modified polyolefin defined as a random, block or graft olefin copolymer having functional groups selected from the class consisting of carboxylic acid, carboxylate ester, carboxylic acid anhydride, carboxylate salts, amide, epoxy, hydroxyl and acyloxy. The blends are described as soft, flexible compositions having high tensile and tear strength with good processability and good adhesion to a wide variety of plastics. Applications include fabric coatings for upholstery, rainwear and sportswear and for production of surgical gloves, plastic laminating and the like.
EP 0353673 A1 describes blends of a thermoplastic polyurethane elastomer and a carbonyl modified polyolefin with improved properties such as impact resistance, low temperature toughness, low melt processing temperatures, generally increased flex modulus and improves flex strength. The amount of carbonyl modified polyolefin is generally about 1 part to about 30 parts by weight for every 100 parts by weight of the thermoplastic polyurethane elastomer. The blends can be used to produce heat molded products for automotive applications.
EP 2279767 A2 describes a medical device, in particular a urinary catheter, comprising a substrate, having on its surface a hydrophilic surface layer providing a low friction surface when wetted by a wetting fluid. The substrate is made of a polymer blend comprising a polyolefin and a composition having molecules with active hydrogens, such as polyamide or polyurethane. The preferred blend comprises at least 80 weight percent polyolefin and therein possibly intermixed medical oil and/or paraffin, and 2-20 weight percent of the component having molecules with active hydrogens. This composition is described as environmentally acceptable and cost effective, has adequate mechanical and chemical properties, and enables the hydrophilic coating to be adequately adhered.
UK Patent Application No. GB 2048903 describes a thermoplastic resinous composition consisting essentially of 5 to 70 weight percent of a thermoplastic polyurethane elastomer and 30 to 95 weight percent of a modified polyolefin or an olefin copolymer, having functional groups of at least one type selected from carboxyl, carboxylate salt, carboxylic anhydride, amide, hydroxyl and epoxy groups. An application of the thermoplastic resinous composition is a laminate having at least two layers bonded to each other, at least one of the layers being comprised of the above-mentioned resinous composition.